Geotubes, the Effective Solution for Sludge Dewatering

Indian cities and industries produce more sludge every year as populations grow and treatment plants are added, and most of it is mostly water. Hauling or storing that water is expensive. Geotubes, large tubes of high-strength geotextile, are a low-cost way to separate the water from the solids on site.

What is dewatering?

Dewatering means removing water. It is common in construction and in the wastewater treatment industries, where it means removing liquid from sludge or slurry. Power plants, refineries, municipal and industrial wastewater treatment plants, and sites handling hazardous or nuclear waste all dewater their sludge.

Why is dewatering necessary?

Sludge dewatering separates the solids from the liquid in a sludge or slurry. The aim is to shrink the volume of waste, remove free liquid before disposal (most landfills will not accept it), and cut the cost of storage, transport and disposal.

Geotubes, The practical solution for dewatering sludge:

What are Geotubes?

Geotubes are large containers sewn from high-strength, permeable engineered geotextiles, usually woven polypropylene. They dewater large volumes of contaminated wastewater or sludge at low cost.

They are made to size for each project, work outdoors in most weather, have no moving parts and need little maintenance. Because there is no press or centrifuge to run, they use far less energy than mechanical dewatering.

The main functions of the Geotubes are:

• Containment: the solids are held inside the tube.
• Dewatering: free water drains out through the fabric, reducing the waste volume.
• Consolidation: the remaining solids keep drying and densifying over time.

How do they work?

Dewatering of sludge with Geotubes is a three-step process:

Filling and Thickening: The dredged material or sludge is pumped into the Geotube. A polymer flocculant dosed into the feed line binds the fine solids into flocs, so they separate from the water quickly and are held back by the fabric.

Dewatering: Free water drains out through the pores of the geotextile, and the volume in the tube falls, so it can be filled again. The filtrate is usually clear. Depending on its quality and the local discharge consent, it is either treated further, returned to the plant, or discharged.

Consolidation: After the last fill, the solids in the Geotube keep drying and densifying. A sludge pumped in at a few per cent solids that ends at 20–30% solids has lost close to 90% of its volume. The Geotube is then cut open and the solids are taken away for disposal or reuse.

Geotubes are also used in ports and harbours, coastal protection, dams and levees, and for landfill waste and sludge lagoon clean-up.

Recovering the filtrate also returns water to the plant. Geotube dewatering is simple and cheap to run, and with no mechanical equipment it is much quieter than a belt press or centrifuge.

To size Geotubes for a sludge, Ocean Geosynthetics needs the sludge type, solids content and daily volume, and the space available on site. Contact the team with these details for a recommendation.